World number seven Jelena Ostapenko was stunned by Estonia's Anett Kontaveit in the third round of the Australian Open.
The French Open champion was beaten 6-3 1-6 6-3 by world number 33 Kontaveit in one hour and 53 minutes.
Kontaveit drew a series of errors out of her former junior doubles partner, but Ostapenko recovered to force a deciding final set.
However she was overpowered by Kontaveit, who will play Spain's world number 39 Carla Suarez Navarro next.
Ostapenko's exit means that Angelique Kerber and Maria Sharapova - who play each other on Saturday - are the only two Grand Slam champions remaining in the women's draw.